something snapped... rear end of 2001 silverado

Truck sat for 10 days. Put it in reverse and it wouldn't move. Gave it a little gas and something snapped in the left rear wheel. Now it turns but all of the power is to the right wheel, as left just spins freely.

I have a '85 Silverado and I think I broke the pinion gear in the rear end but i'm not 100% sure. I was going about 20 and romped on it hard and then i heard a bang and grinding noise from the back ...